1. Field of the Invention
The present invention relates to improvements in access control and particularly to enhancing the security of locking systems by requiring that a pair of differently formatted access codes be simultaneously delivered to and recognized by a locking mechanism in order to cause the operation thereof. More specifically, this invention is directed to a hybrid security device, and especially a cylinder lock, which may be operated only when a properly bitted mechanical key is inserted in the keyway of the plug portion of the lock and an encoded electrical signal is simultaneously transmitted to and recognized by the device whereby one or more pin tumbler stacks which are not operated by the mechanical key will be displaced to the unlocked position. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
Mechanical locks which afford an exceptionally high degree of security, i.e., locks which are exceedingly difficult to defeat, are well known in the art. An example of such a lock, which is of the cylinder type, may be seen from FIG. 1 of U.S. Pat. No. 4,823,575. In situations where a high degree of security is required, locks of the type shown in U.S. Pat. No. 4,823,575 are desirable because the security offered by the lock may be enhanced by periodic replacement of the cylinder or plug portion of the lock, i.e., the lock may be rekeyed. There are, however, many applications where the security afforded by a lock which is responsive to a single access control device, such as a key operated mechanical lock, is considered insufficient.
Electromagnetically activated security devices have also previously been proposed and, in some cases, actually constructed and installed. These electromagnetically activated devices have employed a solenoid and associated plunger to perform a latching function, i.e., either the solenoid plunger functioned as a bolt or the state of energization of the solenoid determined whether a bolt could be moved. Examples of prior art electromagnetically activated security devices may be seen from U.S. Pat. Nos. 4,603,564, 4,730,471, 4,761,976 and 5,140,317. The prior art electromagnetically activated security devices were generally characterized by volumetric inefficiency, the possibility of defeating the lock upon accidental or deliberate disabling of the solenoid actuator and by the use of a single access control device.
Electronic access control systems, i.e., systems which switch power to a solenoid of an electromechanically activated security device in response to recognition of an electronically transmitted access code, are also well known in the art. The more sophisticated of such electronic systems have the desirable attribute of a programmable access code. Some of the previously available electronic access control systems include mechanical keys having built-in electronics for providing a coded signal which is recognized, and responded to, by circuitry included within the cooperating lock. Such electronic access control systems have previously been sold by the assignee of the present invention under the trademarks "KABA NOVA" and "LEGIC".
Security systems have also been proposed wherein a single key, with built-in electronics, may be utilized to operate either a mechanical lock of the type disclosed in U.S. Pat. No. 4,823,575 or an electronic access control. Such systems could theoretically enhance security by requiring serial operation of mechanical and electronic locking devices.
The prior art has not provided a locking system wherein all of the protective features of both mechanical and electronic locks were incorporated into a single, volumetrically efficient locking device which, in order to be actuated from a locked to an unlocked condition, would have to substantially simultaneously recognize both a mechanical code, in the form of key cross-sectional profile and bitting, and an electronic code transmitted to the lock in some suitable manner. Such a highly desirable locking system would also be characterized by an inability to defeat the lock by disabling the electronic control, and particularly the electromagnetic actuator associated therewith, or by "picking" the mechanical lock.
It is to be noted that locking systems have previously been proposed which require the simultaneous presentation of two control devices in order to permit access. In a basic form, such systems are embodied in conventional safe-deposit boxes which require two mechanical keys to be simultaneously operated to afford access. Such prior locking systems which require plural simultaneous control actions, however, have typically also required the use of dual locks or have resorted to blocking motion of the bolt, as opposed to immobilizing the plug portion of a rekeyable cylinder lock, as one of the two locking mechanisms. Bolt immobilization is inefficient, relatively easy to defeat and relatively expensive from both a manufacturing and installation viewpoint. There has not previously been a locking system which, for operation, required the substantially simultaneous use of two dissimilar devices which are brought together to, in effect, form a composite key which would be used solely for the purpose of gaining entry, the two devices thereafter being maintained under the control of different individuals.